"A lámpák amik a falon vannak, szépek" should be accepted. Reported.
Well, I'm not sure any more. Ami and amely are used differently.
(I found this, for example http://forditas.fsf.hu/html/node5.html)
But in real life I think a lot of people use "ami, amik" in sentences that could work with "amely, amelyek".
Why is the following wrong? "A lámpák szépek, amik a falon vannak."
If you don't have the relative clause right after the noun, I believe you need a "pointer" of some kind -- e.g. Azok a lampák szépek, amik a falon vannak.